Cassettes for processing biological specimens are well known. For example, U.S. Pat. No. 4,220,252 issued Sep. 2, 1990 to Beall et al. describes such a container wherein a perforated receptacle is attached through a frangible hinge portion to a perforated cover. When the cover is rotated about the hinge to mate against the receptacle, the detent means on the cover become inter-engageable with abutment means on the receptacle to hold the cover and receptacle in removable mating relationship.
U.S. Pat. No. 4,421,246 issued Dec. 20, 1983 to Schultz et al. describes a tissue cassette having an open top perforated base adapted to receive a tissue specimen and a perforated lid adapted to cover the base. In the open position, the base and lid are secured together through one or more gates which will break when flexed.
U.S. Pat. No. 4,997,100 issued Mar. 5, 1991 to Dudek describes a unitary biological processing apparatus wherein a perforated receptacle with two arc-shaped abutments and a third hook-shaped abutment is attached through a frangible hinge portion to a perforated lid with two arc-shaped detents at the two edges of the lid.
All of the above cassettes have frangible portions which must be broken once the specimen is placed in the base so that the lid may be secured to the base. The advantage of having a hinge portion is that the lid remains connected to the base until use is required to retain a specimen. However, some disadvantages exist. For example, in some cases, the frangible portions are too thin and will break before the lid is secured in place. In other cases, the frangible portions are too thick and will not fold easily.
Also, on most cassettes having a lid with a tab, the latter extends over the front angled face of the base, thus limiting the area on which data relating to the specimen may be inscribed or read.